Apparatus for and method of manufacturing electric discharge devices



Marek 13, 1934. TCE, FOULKE 1,951,142

APPARATUS FOR AND METHOD OF MANUFACTURING ELECTRIC DISCHARGE DEVICES 4 ATTORNEY March 13; 1934. T E, FOLKE 1,951,142

APPARATUS EoR AND METHOD oF MANUFACTURING ELECTRIC DISCHARGE DEVTCES Filed Oct. 28. 1932 'fsheets-Sheet 2 To PUMP No.3 4 42 40 TO PUMP A N /1 NO'Z E 50 r 41 ,I z@ 58 s I l Il I 55 1 To LEAK A? 58 DETECTOR v4v @1 ToNFulr/IP /l I (g /l Il ll'l A DRY-Am. To PUMP NOA. NEON INVENTOR BY e W ATTORNEY March 13, 1934. T E, FOULKE 1,951,142

4 APPARATUS FOR AND METHOD OF MANUFACTURING ELECTRIC DISCHARGE DEVICES Filed OCT.. 28. 1932 3 Sheets-Sheet 3 INVENTOR I I, @W l TToRNEY Patented Mar. 13, 1934 UNITED STATES PATENT oFFicE APPARATUS FOR AND METHOD OF MANU- FACTURING ELECTRIC DISCHARGE DE- VICES Application October 28, 1932, Serial No. 640,074

8 Claims.

The present. invention relates to electric discharge devices and particularly to the manufacture of discharge devices having a gaseous atmosphere therein at a relatively low pressure.

The main object of the invention is to provide an improved method of and apparatus for evacuating the envelopes of gaseous discharge devices or the like, and of introducing the gaseous l atmosphere therein, but other objects and ad- 10 vantages will appear in the course of the followingV specification. The invention consists in a new and original arrangement and combination of steps in the process, and in a new and novel combination of parts in the apparatus, asliereinafter set forth and claimed.

Gaseous discharge devices, particularly of the cathode glow type, are commonly manufactured with a hermetically sealed envelope, within which there is a gaseous atmosphere at a relatively low pressure. It has been found that water vapor, oxygen and other impurities which may be present in these envelopes due to their contact with air during manufacture are exceedingly detrimental to the product, hence great care has been exerf method heretofore in use has been to seal the envelope to an exhaust system, the envelope being enclosed within an oven during evacuation. The occluded gases, water vapor and other impurities were thus driven oi by the combined action of the vacuum and the heating of the walls. After a thorough degassing in this manner, a gaseous filling such as neon, helium, mercury vapor or y the like was admitted and the envelope sealed off.

This method has been slow, and by its nature rendered the uniformity of the product uncertain. Some method of mechanically performing the process, or at least parts of it, both to speed up production and to improve the uniformity of the product has long been sought, but the necessity of maintaining the purity of the gas filling has prevented a successful solution of the problem, since exhaustive experiment has proven that even J the seemingly trivial leakage through the carefully ground rotary valve of an automatic exhaust machine seriously impairs not only the gaseous content of a particular device, but the source, as well. Contamination of the latter is, of course, cumulative, so that the production of lamps of uniform gaseous content with such apparatusis precluded. As a result, the production of these devices on an automatic exhaust machine has heretofore been impossible. I have discovered, however, that such devices can be satisfactorily produced'on an automatic machine of cised in the past to insure their removal. The..

envelopes are carried into an oven where they my invention which has special means incorporated therein to maintain the purity of the gas admitted to the discharge devices. This means takes the form of a highly evacuated ring in the rotary valve of an automatic exhaust machine, about the ports at which the discharge device receives its gaseous filling and at which it is sealed off, so that the leakage is always from said device and from the gas supply system, instead of thereto, as has heretofore been the case. Other precautions, hereinafter described, are also taken to eliminate other sources of contamination. Since by use of this machine each device is treated exactly like every other one, substantial uniformity of product is now obtainable for the first time, and in addition, the cost of manufacture of these devices is materially reduced.

In the manufacture of a gaseous discharge device according to a preferred form of my invention the tubulated envelope is placed upon my new automatic exhaust machine. This machine has an intermittently rotating water cooled head which carries a plurality of oiled rubber tubes which make gas tight connection with the tubulations of the envelopes. As the head rotates the are heated sufficiently to driveoif all occluded gases and water vapor. The rotation of the head thensuccessively' connects the envelope with a succession of ports through which the envelopes are in turn subjected to a rough exhaust, a leak detector, a flushing atmosphere such as dry air, and then to a succession of exhaust pumps of increasing eliiciency. As each envelope nears the point of removal it is allowed to cool until it is at room temperature, and at the last port the exhausted envelope is filled with the desired gaseous atmosphere at a suitable pressure. Means are also preferably provided to test the vacuum on the last pump, and to test the gas purity in the device. At the last rest position the envelope is sealed'off.

In the accompanying drawings, I have shown for purposes of illustration one form of apparatus which I have devised for performing my new process. In these drawings:

Fig. 1 is a plan view of my new exhaust ma'- chine,

Fig. 2 is a similar view of the machine of Fig. 1 105' with parts thereof `removed and the rotary valve partly brokenaway to show the manifold connections, f

Fig. 3 is a detailed plan view of the stationary part of the rotary valve of the machine of Fig.1, 110

Fig. 4 is a sectional View of the rotary valve taken along the line 4 4 of Fig. 3,

Fig. 5 is an elevational view, in part schematic, of the apparatus used to test the vacuum and the gas purity,

Fig. 6 is a sectional view taken along the line 6-6 of Fig. 1, and

Fig. 7 is an elevational view of the leak detecting apparatus.

In these drawings, a bed plate 1 supports a Geneva gear 2 upon a suitable bearing surface. The Geneva gear 2 in turn supports the spider 3 which carries at its outer edge the hollow arcuate segments 4. Water for cooling the segments 4.11ows by gravity from a tan-k 5 centrally supported upon the spider 3 through the pipe 6 to one of the segments 4, thence from segment to segment via suitable tubes, not shown, returning through the pipe 7 to a centrally located point where it discharges into a suitable disposal system'. Water is admitted to the tank 5 by means of a pipe, not shown, from any convenient source.

A motor 8 drives a crank arm 9 in any suitable manner, said'crank arm in turnalternately driving and locking the Geneva gear 2, so that continuous rotation of the motor 8 results in the intermittent rotation of the segments 4 in a counterclockwise direction.

A circular plate 20, which serves as the fixed part of a rotary valve, is mounted on the bed plate 1 concentrically with the Geneva gear 2. and extends through a central opening in said Geneva gear. A similar plate 21 which rests on top of the plate 20 serves as the moving part of the rotary valve. A bar 22 which is loosely secured by means of the pins 23 for rotation with the Geneva gear rests upon the upper surface of the plate 21, engaging said plate for rotation therewith by means of the pins 24, thus causing the valve plate 21 to rotate with the Geneva gear 2. A sleeve 25 maintains the alignment of the plates 20 and 21. The plate 20 has a plurality of ports 26 therein spaced at the same angular intervals as the positions of rest of the Geneva gear 2. one port being omitted. however, at the seal-olf position.` The plate 21 has the correspending ports 27, each of 'which registers with a port 26 at each rest position, except at the sealoff position. A series of oil glands 28 are provided to seal the two plates 20 and 21 ofthe rotary valve against leakage therebetween.

A plurality of openings 30 at the same angular intervals as the ports 26 of the rotary valve extend through the segments 4. Each of said openings 30 has a short length of thick walled rubber tubing 31 snugly fitted therein. each end of the tubing being somewhat compressed by elastic means such as the rubber bands 32, in' order to overcome the tendency of the tubing 31 to eject glass tubing inserted therein. The upper opening of each tube 31 is adapted to receive the tubulation 33 of an lenvelope 34 whichis to be exhausted, the tubulation being preferably greased to make an air tight connection therewith. The lower end of each tube 31 is connected by a tube 35' to a port 27 in the rotary valve plate 21. As a result each envelope 34 is successively connected with each of the ports 26 as the Geneva gear 2 is rotated.

The-connection of these ports 26 will now be described, with special reference to Fig. 2. That port 26 which is connected by the rotary valve to the tube 35 which terminates at the position marked A is connected to a Source 9i dry @ir by the tube 36. Passing in a counterclockwise direction, the next port 26 is connected through tube 37 to a suitably driven vacuum pump, not shown, of capacity sufficient to substantially evacuate all the system connected thereto during the rest intervalof the Geneva gear 2. The third port 26 is connected through a tube 38 to a leak detector, shown in Fig. 7. The fourth port 26, counting from the position A, is connected to tube 37, and thus to the first vacuum pump. The fifth port 26 is connected to the tube 36, and thus to the source of dry air. The next four ports 26 are connected through a manifold 39 and tube 40 to a suitable vacuum pump of suflicient capacity to maintain a high vacuum in the system connected thereto. The next six ports 26 thereafter are connected through a manifold 4l and tube 42 to a vacuum pump capable of maintaining a very high vacuum, preferably a mercury vapor diiuv sion pump in series with a high capacity mechanical pump. The next port 26` is connected by the tube 43 to a pump capable of maintaining an extremely high vacuum, preferably a mercury vapor diffusion pump in series with a suitable mechanical pump. is connected through the tube 44 to a suitable source of the desired gaseous atmosphere, means (not shown) being preferably included in this connection to maintain a desired constant pressure supply.

As shown in Figs. 3 and 4, special means are provided to prevent the impairment of the purity of this gaseous supply system, due to leakage in the rotary valve. A channel 45 which is cut in the upper surface of the valve plate 20 opens into that port 26 which is connected to the last pump, and extends about that port 26 which is connected to the gaseous source and that port 27 in the rotary valve plate 21 which is at the blank seal-olf position. Due to the high vacuum in this channel, it is obvious that any leakage between said valve plates will be away from the protected ports 26 and 27, and that impairment of the gaseous purity is thus precluded. A further advantage of this construction is that each time the valve plate 21 is moved the port 26 which was at the blank seal-olf position is mo- -mentarily connected to the channel 45. The pure gas remaining in the tube 35 and in the sealed-olf tubulation 33 which is connectedto 'l said port 26 is thereupon admitted to the system connected to the last pump, which requires an appreciable interval-to remove it, thus providing a flush of pure gas,v for the envelope 34 which is a moment later connected to said system. An additional flush with pure gas is thus obtained, using gas which would otherwise be lost at a later stage in the operation. In some cases, however, where speed of exhaust is essential,` or where there is a hazard of breakage of the sealed off tube 33, with an attendant inrush of air, the channel 45 may be terminated at an appreciable distance each side of the path taken by the The last port 26 10() ports 26 without allowing appreciable leakage to to the top of said segments, and extends from a point between the rst and second positions counterclockwise from the position A to a point approximately 260 therefrom. Said oven 50 is heated to about 500 C., or higher if permitted by the envelopes 34, by flames from the perforated pipes 51, which are supplied with a suitable mixture of gas and air through the pipe 52. Each end of the oven 50 has a suitable opening for the passage therethrough of the envelopes 34 carried bythe segments 4, and a continuous slit in the bottom of said oven allows passage of the tubulations 33.

The leak detector which is connected to the tube 38 consists, as shown in Fig. 7, of a mercury manometer 55 having contacts therein which are designed to be closed by the mercury whenever the vacuum falls below a predetermined value. An alarm bell 56 and a battery 57'are included in a circuit with the contacts of the manometer 55, the bell 56 thus giving the alarm whenever the vacuum fails, allowing the operator to apply a suitable clamp to the connected tube 31, so as to disconnect the leaky envelope from the system. Since such clamping'means is well known, it will not beA further described here. A tube 58 having a stop cock 59 therein connects the tube 38 with the tube 40, said stop cock normally being closed. When the vacuum is lowered in said manometer 55, due to the connection of a leaky envelope thereto, this cock is temporarily opened, however, whereby the 'manometer is re-evacuated and the mercury therein restored to normal level by means of the.

pump connected to said tube 40. Said leak detector is then ready to check the vacuum of the next device to be connected thereto. f

As a check on the vacuum in the discharge device while in the last stage of the exhaust, and also as a check on the purity of the gaseous filling a high voltage electrical discharge is induced in the envelope 34 at each of these positions by the apparatus shown in Fig. 5. A lber post which is mounted on the bed plate 1 carries on the top thereof a conducting rod 66 which extends directly over the position taken by an envelope 34 while it is connected through the tube 43 to the last stage high exhaust pump, said rod continuing in the general direction of the envelope 34 which is at the gaseous lling position. A exible conductor, such as the chain 67, hangs from this rod 66 and makes contact with the inleads 68 of the envelope 34 which is at the exhaust po-` sition, while a wire 69 depends from said rod 66 adjacent to, but not` in contact with, the constriction in the tubulation 33 of the envelope 34 which is at the gaseous lling position. A lead 70 connects the rod 66 with a high frequency, high voltage source of electricity, such as is schematically illustrated at '71, the other terminal of which is grounded, as is the bed plate 1.

In the use and operation of my apparatus, the automatic exhaust machine being in operation with ames lit, motor running, all pumps operating, and each of the tubes 31 closed either by an envelope 34 or a suitable plug, the envelope or plug contained by each of the tubes 31 is removed as it reaches the position A and the tubulation 33 of an envelope 34 is greased and inserted therein. As the machine rotates the envelope 34 is carried to the first pumping position, which is just outside the oven 50. At the next position of rest the envelope 34 is connected to the manometer 55, so that any leak in said envelope 34 which results in failure to produce or maintain a vacuum therein is audibly indicated by the bell 56. In case of a leak a clamp is immediately applied to close the connected tube 31, after which the stop cock 59 is opened for a brief interval to reset said manometer 55.l In this manner contamination of the gas source, and of the other envelopes 34 which may later be connected to the same manifold, is avoided. At this position the envelope 34 has been carried into the oven 50, the temperature of which is suicient to drive off any gases or vapors which may be occluded in the walls of the envelope 34. At the next movement of the Geneva gear 2 said envelope 34 is again connected through the tube 37 to the rst pump for further exhausting, after which further movement of said Geneva gear 2 connects said envelope with the source of dry air, with which it is ilushed. During the'next ten movements of the Geneva gear this baking out and exhausting of the envelope 34 is continued, so that a high vacuum is produced therein. Further movement of said Geneva causes said envelope to emerge from the oven 50, and to be connected to a final exhaust pump through the tube 43. At the moment of connection this pump system is, however, filled with pureI gas at low pressure, due to the previous momentary connection `of the channel 45 with the port 26 which was at the seal-01T position at the previous period of rest, so that the envelope 34,receives a flushing, after which the envelope is evacuated by said pump. A visual indication of the effect of this pump is provided by the discharge in said envelope due to contact of the leads 68 thereof with the chain 67. This discharge ceases when the desired vacuum is reached; hence its persistence notifies the operator of a defect, a suitable clamp being immediately applied to close the connected tube 31, in order to prevent the contamination of the gaseous source which would otherwise result from thesubsequent connection of the leaky envelope 34 thereto. Assuming the envelope 34 to be fully evacuated, however, the next movement of the Geneva gear causes connection of said envelope to the gaseous source. The purity of the gas admitted to said envelope is also subject to visual inspection, since the color of the discharge induced in the tubulation 33 as a result of the proximity of the wire 69 will vary with the gaseous content. This gas is at a relatively low pressure of the order of 10 to 100 m. m. of mercury, and hence any leakage between the plates 20, 2l of the rotary valve would tend to be from the atmosphere to said envelope and the gaseous supply system connected thereto. The surrounding guard channel 45, however, due to its connection to the high vacuum port, positively precludes any such leakage inwards, it being obvious that any possible leakage will be from the gas system to the guarding channel 45. As a result impairment of the gaseous purity is entirely prevented. Since this impairment of the gas purity was one of the most seriousvof the diiculties which resulted in the failure of prior attempts to exhaust discharge devices of this type on automatic'machines, the value of my new guard ring is apparent. Still further movementy of the Geneva gear moves the lenvelope 34 to the blank position on the valve plate 20. The envelope is then sealed oi in any usual manner.' Contamination of the gaseous content during this process is, of course, prevented by the guard ring 45 which, as shown, surrounds the port 27 which is connected to said envelope 34 which is being sealed off. At the next movement of the Geneva the sealed tubulation 33 is momentarily connected to the channel 45, as previously noted, with a resulting evacuation of most of the gas therein. As the Geneva comes to rest said tubulation is connected to the'source of dry air, relieving the vacuum in the system connected thereto, after which said tubulation is removed from the machine and another envelope 34 'inserted in place thereof. While the envelope 34 was being thus treated other envelopes 34 were being inserted in each succeeding tube 3l as it reached the loading position A, each of which in turn goes through the same cycle as has just been described.

While I have described certain steps of my process as being performed by machine it will be readily understood that where desired these steps may be performed by hand to meet the needs of any particular conditions of manufacture. It will be further understood that while I have used electric discharge devices to illustrate my invention, the proces and apparatus are equally useful in the manufacture of similar articles in which an envelope must be sealed off with a vacuum or a gaseous content of great purity therein.

It is likewise obvious that various other changes,

omissions and substitutions may be made in the steps of the process or in the apparatus without departing from the spirit of the invention.

I claim as my invention:

1. The method of filling devices with an attenuated gaseous atmosphere which comprises connecting said devices through a valve to a source of gas at the desired pressure, and preventing atmospheric leakage through said valve to said gas source by maintaining a zone about the port in said valve at a pressure less than that of the atmosphere.

2, 'Ihe method of filling devices with an attenuated gaseous atmosphere which comprises connecting said devices through a valve in turn to a vacuum system, to a second vacuum system which initially contains some of the desired gas at a low pressure whereby said device is flushed and again evacuated, and then to a source of said gas at the desired pressure, and preventing atmospheric leakage through said valve to said source or to said device after it is filled with said gas by continuously maintaining a zone in said valve about the ports leading to said source at a pressure less than that of said source.

3. In apparatus for filling devices with an attenuated gaseous atmosphere, in combination, a source of gas at the desired pressure, means to feed gas from said source to said device, said means including a valve. and means to prevent contamination of said source by air leakage through said valve comprising means to maintain a zone about sai-d valve at a pressure appreciably less than that of the atmosphere.

4. In apparatus for lling devices with an attenuated gaseous atmosphere, in combination,

a source of gas at the desired pressure, means to feed gas from said source to said device, said means including a valve comprising two members having cooperative faces with ports therein, a channel in one of the faces of said valve, said channel substantially enclosing the port to which said source is connected, and means to maintain the pressure in said channel at a value less than that of said source.

5. In apparatus for filling devices with an at'- tenuated gaseous atmosphere, in combination, a source of gas at the desired pressure, means to feed gas from said source to said device, said means including a rotary valve comprising two members having cooperative faces with ports therein by which said device may be connected in succession to an exhaust pump and to said source, and a channel in the face of said valve on each side of and beyond the port leading to said source, said channel being connected to said exhaust pump.

6. In apparatus for lling devices with an attenuated gaseous atmosphere, in combination, a source of gas at the desired pressure, a valve having two members with cooperative faces movable with respect to each other, a series of ports in one of said members to each of which one of said devices may be connected, and a series of registering ports in the other of said members, one of said ports being connected to a vacuum system, an adjacent port being connected to said gas source, and a channel in the face of the latter member connecting with the` rst of said ports therein and extending about the latter of said ports.

7. In apparatus for filling devices with an attenuated gaseous atmosphere, in combination, a source of gas at the desired pressure, a rotary valve comprising two members having cooperating faces movable with respect to each other, a series of ports in one of said members to each of which one of said devices may be connected, and a series of registering ports in the other of said members, one of the latter ports being connected to a vacuum system, the next port being connected to a separate vacuum system, while the next port thereafter is connected to said source of gas. after which there is a blank position in said latter member, and a channel in the face of the latter member which connects with the second mentionedr port therein and which extends on either side of the port connected to said gas source and about said blank position.

8. A rotary valve comprising two members having faces cooperating with each other and having registering ports, a channel in the face of one of said members substantially enclosing one of said ports and having no connection therewith, and means to evacuate said channel.

TED E. FOULKE. 

